The only four stroke you'd fit in there would be some of the new generation Saito's. They are really narrow and light. My 82 in my Wot 4 is the same mounting dimensions as your 46 and 10 grams lighter than a 55AX. Power is much the same as your 46 if you were allowing your 46 to rev to 17000 revs, but who does that.
This is what I've been doing. Mounting a REAL ENGINE to the 'Quickie' (as it is labeled inside) which I bought from the club, as part of the donations by Lindsay recently (see website for other tender items). $30 three-channel model now with a AP 15 in the nose. Flew it for the first time on Friday, from our orchard. Nice and quiet, but not a power house. Not easy to tune, as it doesn't have a low-speed needle. The high-speed needle does affect the low speed, so a compromise is all I can get. Good enough for my boys to train with. Better than a Bixler, as the ESC overheats running at part throttle all the time.
Everyone knows that REAL ENGINES are used by REAL men. Eklectic motors are best left for use in toothbrushes and other unnecessary things.